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In this paper, a homogenized multiphase lattice Boltzmann (LB) model is established for parallelly simulating immiscible two-phase flow in both solid-free regions (pore scale) and porous areas (continuum scale). It combines the color-gradient multiphase model with the Darcy–Brinkman–Stokes method by adding a term that includes surface force and drag force of porous matrix to multiple-relaxation-time LB equation in moment space. Moreover, an improved algorithm is proposed to characterize and implement the apparent wettability in the locally homogenized porosity field. Validations and test cases are given to demonstrate the accuracy and robustness of this new model, as well as its applicability for trans-scale fluid simulation of transport and sorption behavior from porous (Darcy flow) area to free (Stokes flow) area. For practicality, the two-phase seepage flow in a composite rock structure with multiscale pores is simulated by this new model, and the effects of viscosity ratio and wettability on the displacement process are discussed. [ABSTRACT FROM AUTHOR]

Immiscible two-phase flow in porous media is crucial in various industrial processes, necessitating a robust numerical tool to capture this complex multiscale behavior. This paper aims to introduce a novel micro-continuum multiphase solver, abbreviated as DBS-CG, which integrates lattice Boltzmann method with the Darcy–Brinkman–Stokes approach via embedding a volume-averaging scheme into the color-gradient model. The fluid–solid interactions in free and porous regions are effectively reproduced by the continuum surface force and micro-capillary force incorporated in DBS-CG. Validations against analytical solutions and numerical experiments confirm that DBS-CG is capable of monolithic modeling the trans-scale immiscible flow in spatially fluctuated porosity fields. Additionally, the water–oil displacement processes in mix-wetted and fractured–vuggy porous systems are tentatively investigated by DBS-CG, where various fingering patterns and preferential flow paths under different structural conditions and fluid properties are discussed. Non-monotonic trends of the recovery efficiency indicate that this multiphase process is competitively manipulated by the capillary or Darcy drag forces in microporous regions and inertial or viscous forces in solid-free regions, and thus, the moderate wettability and sedimentation are more beneficial for oil extraction. [ABSTRACT FROM AUTHOR]